1-Azido-1,1-dinitroalkanes, useful as propellants

ABSTRACT

Azido nitro paraffin, a method for its preparation by electrolysis of the corresponding nitroparaffin salt and sodium azide and its uses as a plasticizer, propellant or propellant component.

United States Patent 1 Wright May 13, 1975 l-AZIDO-1,1-DINITROALKANES, USEFUL [56] References Cited A5 PROPELLANTS UNITED STATES PATENTS [75] Inventor: Charl s M- Wright, Wilm ng n. 3,357,959 12/1967 Jabloner 260/80 D I. A U d S A OTHER PUBLICATIONS [73] ssignee: e nite tates o merica as represented by the Secretary of the Jr. et al., Chem. Reviews, Vol. 64, pp. 4l to 44 Navy, Washington, DC.

[22] Filed: 1968 Primary ExaminerLeland A. Sebastian [21] Appl. No.2 780,614

[57] ABSTRACT [52] US. Cl. 149/88; 149/92; 204/72; Azido nitro paraffin, a method for its preparation by 260/349 electrolysis of the corresponding nitroparaffin salt and [51] Int. Cl. C06b 15/02; C070 1 17/00 sodium azide and its uses as a plasticizer, propellant or [58] Field of Search 149/88; 260/349, 32.4; propellant component. 204/72 8 Claims, No Drawings l-AZIDO-l l -DINITROALKANES, USEFUL AS PROPELLANTS BACKGROUND OF THE INVENTION This invention relates generally to an energetic composition, a method for its preparation and its uses. More particularly, it relates to azido gemdinitroparaffin. The nitro alkanes are commonly regarded as being a good source for energetic material and this particular nitroalkane is of special interest because its relative insensitivity to impact and thermal stability makes it a good choice as a propellant or as a component in a propellant system.

The process of making azido compounds has always caused chemists difficulty especially when the reaction is an attempt to add reactive groups to an already reactive and unstable compound. In the past, this reaction, if it proceeded at all, was likely to result in an explosion. 1

SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide an energetic material which is relatively insensitive to impact and is thermally stable.

Another object of this invention is to provide a method of preparation of an energetic material with the aforementioned properties.

A further object is to provide a plasticizer for a polymer.

Still another object of this invention is to provide a propellant composition.

According to the invention these and other objects are attained by providing a new class of compounds which are represented by the following structural formula:

where R is a straight or branched chain containing up to approximately eight carbons including lower alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl and pentyl among others. The method or preparation for the various energetic compounds consists of reacting a salt of the gem-dinitroparaffin with an azide in an electrolysis cell. For example, a salt having the formula where R is aliphatic and contains up to eight carbons is reacted with an acid to form R CH(NO whereupon an azide in a basic solution is added thereto and the resulting solution is then electrolyzed to form the desired compound.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the compounds may be prepared as described above, there are some recommended steps to be followed if a good yield is desired. For example, in order to obtain a relatively pure stating material, the dinitro salt may first be made as a salt which is insoluble in water such as the potassium salt the preparation of which was previously reported by C. M. Wright and D. R. Levering in Tetrahedron 19 Supp. 1, 3 (1963). Another method of preparation for the potassium salt which can be used was suggested by Dr. Levering who used l-chloro-l-nitroethane as a reactant in the Ter- Meer Process.

The limited solubility of the potassium salt which allows it to be prepared in a relatively pure form is disadvantageous in that it does not react effectively with the azide. But, it was found that the soluble dinitro salt does produce the azido derivative in good amounts and therefore, in the practice of this invention the potassium salt is converted into the soluble sodium salt. This may be accomplished by first converting the potassium salt into the dinitroalkane by the addition of hydrochloric acid and then reacting the alkane with the azide in a sodium hydroxide solution.

The products and processes of the invention are further described and illustrated by the examples hereinunder set forth.

EXAMPLE I The potassium salt of l,l-dinitroethane was prepared according to the Wright and Levering method which has already been disclosed. This salt was then converted to 1,1-dinitroethane in approximately yield by the addition of aqueous 5% HCl and extracting with chloroform. A 10% I-ICl solution can also be used although the yield of the alkane was less than with the 5% solution.

A lOO ml aqueous solution of approximately 7% of the dinitroethane was adjusted to pH of approximately 8 with NaOH and 5% solution of sodium azide. The solution was then electrolyzed at a current of 3 amps. for 1 hour in a conventional electrolysis cell having a smooth platinum anode. The electrolysis was stopped every [5 minutes, the product l-azido-l ,ldinitroethane (DNZE) removed and the electrolysis retrarted The crude electrolysis product was then purified by preparative-scale gas chromatography. The electrolysis proceeded smoothly and the overall yield was about 25%.

EXAMPLE II The procedure followed with the propane derivative was substantially the same as described above except that the starting material was the potassium salt of dinitropropane prepared according to the Wright and Levering method. 15.3 g of the resulting yellow crystals were neutralized with 500 ml. of 5% HC] solution. Some of the salt formed did not dissolve and was removed and dried by vacuum (6.79g. obtained purity 99.7% by G.C.). The HCl solution was extracted with three lOO-ml portions of chloroform which was removed and 4.2g of dinitropropane (DNP) (95.8% by G.C.) was recovered at 91% yield. Eight ml. of DNP was dissolved in ml. of distilled water with the aid of NaOH resulting in a pH of 0.2. Then 7.5g% sodium azide was added. This solution was then placed in an electrolysis cell in which the dinitropropane solution prepared above was used as the anode solution and a few milliliters of 1% NaOH was added to the cathode compartment to serve as a catholyte. The entire assembly was immersed in an ice bath and a current of 3 amps. was passed through the solution. Electrolysis was stopped every 15 minutes and the product which had been formed was removed from the cell. This was continued until no appreciable product formed during a 15 minute period. The total electrolysis time took 1.5 hours and yielded 4.34 grams of l-azido-l,ldinitropropane (DNZP) which constituted 27% yield based on the amount of DNP at the start and assuming that these is no recoverable DNP in the anode solution. This product analyzed 81% pure by gas chromatography.

EXAMPLE 111 A sample of 3 parts of DNZP (Example 11) was mixed with 1 part of polynitropropene. The propane derivative plasticized the polymer. A differential thermal analysis was run and the mixture was found to be stable to over 120C.

EXAMPLE IV TABLE 2. NC Al HMX DNZP DNZE NG NDPA 1 l. 16 44 30 275.8 2. l0 18 42 30 278.1 3. l0 18 42 Run number 5 in the Table sets forth that DNZE exhibits a high I which indicates that it would also be good monopropellant as well as a plasticizer and a component in a propellant composition.

PROOF OF STRUCTURE The structure of the azide dinitroparaffins was proven by a combination of infrared, nuclear magnetic resonance (NMR), gas chromatography and elemental analysis. For example, a purified sample of l-azido-l ,1- dinitroethane (Example I) yielded an NMR spectrum of a single peak at 130 cycles/sec. due to the CH the only protons in the sample. The same sample, on analysis was found to contain 43.4% N (theoretical 43.5%). Infrared showed complex absorption in the azide region, bands at 2,117 emf, 2,150 cm. and 2,190 emf, and strong absorption in the nitro region (1,588 emf). Gas chromatography indicated that the sample contained only one major component that accounted for more than 98% of the sample. These data thus proved the structure of the resultant product.

PROPERTIES OF THE AZlDO DINITROPARAFFINS Both the ethane and the propane derivatives are dense, oily and faintly yellow liquids. One milliliter of the ethane derivative was found to weigh 1.456g at room temperature and boils at 44C (l.75mm.). Also both compounds are extremely irritating to the eyes, nose and skin even in small quantities and therefore find use as a tear gas. In addition, these compounds exhibited relative insensitivity to impact. For example, the ethane has a sensitivity of approximately cm (2-kg. weight, 50%) and the propane a sensitivity of approximately 100 cm. (Z-kg. weight, 50%). On differential thermal analysis (DTA), both compounds were found to be stable to over 100C at a heating rate of lO/min. The Examples set forth herein for the preparation of the azido dinitroparaffins were performed with a smooth platinum. However, anodes made from other materials such as graphite or nickel can be used without departing from the scope of the invention. In addition, the aqueous solutions of the Examples can be replaced by solutions containing other solvents such as methanol or acetonitrile and the electrolysis process would produce the same product.

As will be apparent to those skilled in the art, various other modifications of the invention can be made or followed in view of the above disclosure without departing from the spirit and scope of said invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A compound of the structure v O/N\OK+ where R has the same significance as in claim 1 with hydrochloric acid to form RCl-l(NO adding sodium azide in a basic solution; and electrolyzing the solution. 8. The method of plasticizing polynitropropene by adding to said polymer the compound of claim 1. 

1. A COMPOUND OF THE STRUCTURE R-C(-NO2)-N3 WHEREIN R IS ALKYL AND CONTAINS UP TO EIGHT CARBONS.
 2. A compound according to claim 1 wherein R is lower alkyl.
 3. 1-azido-1,1-dinitroethane.
 4. 1-azido-1,1-dinitropropane.
 5. A method of making an azido gem-dinitroparaffin which comprises the steps of reacting a soluble salt of the gem-dinitroparaffin with sodium azide in an electrolysis cell.
 6. A method according to claim 5 wherein the electrolysis cell contains a smooth platinum anode.
 7. A method of preparing the compound of claim 1 which comprises the steps of reacting
 8. THE METHOD OF PLASTICIZING POLYNIRROPROPENE BY ADDING TO SAID POLYMER THE COMPOUNDD OF CLAIM
 1. 